2007 Acura TSX - Powertrain

The TSX is a precisely engineered sports sedan that blends agility and handling with 5-passenger comfort. That delicate balance of attributes drove every aspect of development, including the selection of the powertrain. When it came to choosing a powertrain configuration for the TSX, the path soon became clear. A V-6 like that in the TL would deliver abundant power, but would increase the size and weight of the car, and move the TSX away from its sporting intentions. An in-line 4-cylinder, using the latest Acura technologies, would make for a lighter, well-balanced, more compact vehicle that puts the emphasis on overall sporting performance and handling responsiveness.

Power for the 2007 TSX comes from an advanced 2.4-liter DOHC i-VTEC™ in-line 4-cylinder that produces 205 hp SAE net (Rev 8/04). With an i-VTEC™ "intelligent" valve control system that features Variable Valve Timing and Lift Electronic Control (VTEC) combined with Variable Timing Control (VTC), the TSX engine delivers formidable power, impressive fuel economy and very low exhaust emissions.

The TSX is offered with either a 6-speed close-ratio manual transmission or a 5-speed SportShift automatic. The manual gearbox features a lightweight magnesium alloy case and multi-cone synchronizers. This transmission has a light, quick action and very short shift throws.

The 5-speed SportShift automatic can function as a conventional automatic transmission or, at the driver's option, can be shifted manually for hands-on sporting fun. Working in combination with the drive-by-wire throttle system, the SportShift transmission's shift logic results in quick, smoothly controlled shifts.

The TSX also features the innovative Maintenance Minder System, which automatically monitors the vehicle's unique operation condition to indicate to the driver when maintenance is required. This system is designed to eliminate unnecessary maintenance procedures to help reduce environmental impact and operating expenses, while ensuring that important service issues are addressed in a timely manner.

The TSX features the latest iteration of the Variable Valve Timing and Lift Electronic Control (VTEC) system. By varying valve lift based on key engine parameters, VTEC lets the engine develop strong low-end torque and exceptional high rpm power. The TSX engine features the "intelligent" i-VTEC system. This "intelligent" system adds VTC (Variable Timing Control) to VTEC to provide continuously variable camshaft timing. By allowing the valve lift and valve timing to be adjusted to suit the engine's operating parameters from moment to moment, i-VTEC provides substantial performance, efficiency and emissions improvements.

VTEC (Variable Timing and Lift Electronic Control)

VTEC is an innovative system that adjusts the lift and opening duration of the valves to help the engine produce strong low-rpm torque and excellent high-rpm power. At low rpm, VTEC automatically adjusts valve timing and lift for optimum cylinder filling. In this low rpm mode, the timing of the intake valves is staggered and their lift is asymmetric, which creates a swirl effect within the combustion chambers. With better mixing in the cylinders, burn speed and combustion stability are improved. As engine rpm builds, VTEC transitions to a high-lift, long-duration cam profile for improved high-rpm engine output.

The TSX uses a variation of this technology with three rockers operating each pair of intake and exhaust valves in each cylinder; the TSX powerplant varies the opening lift and duration of the intake and exhaust valves. At low rpm, the valves follow low-lift, short duration camshaft profiles to help boost low-end torque. Above 6000 rpm, the intake and exhaust valves are operated by high-lift, long-duration cam profiles, for maximum high rpm horsepower.

The powertrain control unit monitors cam position, intake manifold pressure and engine rpm, and then commands a VTC actuator to advance or retard the intake cam, optimizing engine output and reducing emissions. At idle, the intake cam is almost fully retarded to deliver a stable idle and reduce oxides of nitrogen (NOx) emissions. The intake cam is progressively advanced as rpm builds, so the intake valves open sooner and valve overlap increases. This reduces pumping losses, which increases fuel economy and further reduces exhaust emissions due to the creation of an internal exhaust-gas recirculation effect. By continuously optimizing the amount of intake cam advance or retard based on the operating conditions, the TSX engine is both powerful and exceptionally flexible.

CYLINDER HEAD / VALVETRAIN

The cylinder head is pressure-cast aluminum alloy and features four-valves-per-cylinder driven by dual overhead cams. An automatically adjusted silent-type chain drives the cams; it is maintenance free and runs in an oil bath for maximum durability. The combustion chambers have large "squish" areas to promote faster flame propagation and more complete burning-factors in reduced carbon monoxide (CO) and hydrocarbon (HC) exhaust emissions.

CRANKSHAFT, ENGINE BLOCK AND OIL PAN

The TSX uses a forged-steel crankshaft with a relatively long 99mm throw. To reduce friction and improve long term durability, the crankshaft journals are micropolished. The die-cast lightweight aluminum block has cast-in iron cylinder liners with 87mm bores. The liners are made using a spin casting, centrifugal process. To maximize the rigidity and minimize noise and vibration, the block is a 2-piece design that fully supports the five main bearings with a single cast-alloy bed-plate assembly.

PROGRAMMED FUEL INJECTION (PGM-FI)

The i-VTEC 4-cylinder engine features Programmed Fuel Injection (PGM-FI), which relies on an array of sensors to constantly monitor a number of critical operating variables. The system tracks throttle position, intake air temperature, water temperature, ambient air pressure (altitude), intake manifold pressure, exhaust/air/fuel ratios and the position of the crankshaft and camshaft. High-efficiency air-assisted fuel injectors deliver fuel to each cylinder. These multi-hole injectors direct fuel around the intake valve stem for improved atomization, better power output and reduced emissions.

TUNED INTAKE

The TSX uses a single-stage intake manifold that is specially tuned for the engine's power characteristics. Fixed-length intake runners are tuned in length, size and shape to provide an optimal blend of low-rpm torque and high-rpm response, while supporting the advanced i-VTEC valve control system.

EXHAUST SYSTEM

Exhaust flow is critical to performance and figures heavily in the strong power characteristics of the TSX. The high-flow rear-mounted exhaust manifold is constructed of stainless steel. Downstream, large pipe sizes increase flow and the system splits to feed into free-flowing dual silencers and exhaust tips.

DRIVE-BY-WIRE THROTTLE CONTROL SYSTEM

An electronic drive-by-wire system helps enhance the driving character of the TSX. With smart electronics connecting the throttle pedal to the throttle butterfly in the intake tract, the engine response can be optimized to suit the driving conditions and to better match the driver's expectations. By eliminating the direct throttle cable connection to the engine, the ratio between pedal movement and throttle butterfly movement can be continuously optimized. This adjustable "gain" between throttle and engine is a significant step forward in drivability.

To establish the current driving conditions, the system monitors pedal position, throttle position, vehicle speed, engine speed, calculated road slope and corner radius and engine vacuum. This information is then used to define the throttle control sensitivity.

From the driver's standpoint (because the drive-by-wire system is combined with other functions such as VSA and Traction Control) this means that the way the TSX responds to throttle pedal movements is tailored to the driving conditions. In stop-and-go driving, the pedal response has low gain and is smooth and progressive for easy driving. A similar low-gain response makes starting out on snowy or icy roads more predictable. In low- to medium-speed driving conditions, the gain increases to improve response and acceleration. In high speed driving, the gain increases further still, so that there's ample response for passing. The system also alters response based on the road slope, providing more throttle gain on uphills, and less on downhills, and also reduces changes in gain on curvy roads to make the car easy to control.

The throttle system works with the available SportShift 5-speed automatic transmission to make shifts faster and smoother than has been possible before. By coordinating the throttle opening with the transmission's shifting functions, engine power can be precisely tailored to the needs of the transmission at every point during the shifting process. That means less shift shock and delay, no matter the driving situation.

The TSX uses a DC motor to control the throttle butterfly position in the intake tract. Large bearings and superior internal components give the motor greater resistance to vibration.

EMISSIONS CONTROL

As automotive emissions standards tighten, a trend toward decreased power output is the natural result. The challenge with the TSX was to advance power output while simultaneously reducing emissions. The payoff for these efforts was a strong 83 horsepower per-liter peak output, coupled with compliance with some of the toughest emissions regulations in America, the California Air Resources Board (CARB) LEV-2 standard. Compared to LEV-1-LEV, this stricter standard mandates a 75-percent reduction in NOx level and extends the emissions compliance/useful life by 20 percent, to 120,000 miles.

CALIFORNIA EMISSION STANDARDS (gram/mi.)

LEV-1

Tier 2-Bin 5
LEV-2 (TSX)

50,000 mi.

100,000 mi.

50,000 mi.

120,000 mi.

CO (g/m)

3.4

4.2

3.4

4.2

NMOG (g/m)

0.075

0.09

0.075

0.09

NOx (g/m)

0.20

0.30

0.05

0.07

*NMOG = Non Methane Organic Gas

The foundation for exceptional emissions performance was laid by the basic architecture of the TSX. The exhaust port and exhaust system are positioned to the rear of the transversely mounted engine. This means the catalytic converter can be positioned closer to the engine than is possible with a conventional front-exhaust configuration that sweeps under the engine to reach the converter. With the under-floor catalyst, light-off of the multi-cell converter is quick after starting. A low heat-mass stainless steel exhaust manifold also speeds converter light-off.

The i-VTEC cylinder head plays a large role in emissions reduction as well, by fostering internal exhaust gas recirculation, which cuts NOx. Air-assisted fuel injectors reduce hydrocarbons after starting, while a Linear Air/Fuel sensor positioned in the exhaust system just upstream of the catalyst improves air/fuel mixture control.

NOISE, VIBRATION AND HARSHNESS (NVH) CONTROL

The high output in-line 4-cylinder engine features comprehensive NVH reduction features. The pressure-cast block with its bed-plate type main bearing cap is a highly rigid assembly, helping to resist vibration. A pair of chain-driven balance shafts further smoothes the inherent vibration of a large displacement in-line 4-cylinder layout. A self-adjusting silent-type camshaft chain and a serpentine accessory drive belt also reduce NVH.

100,000 OR MORE TUNE-UP INTERVALS

With a self-adjusting silent-type cam chain, long wearing platinum-tipped spark plugs and a precision-engineered valve train, the TSX is engineered for low maintenance. Other than routine fluid changes and inspections, the first scheduled engine tune-up is not required for 100,000 miles or more.

MAINTENANCE MINDER SYSTEM

To eliminate unnecessary service stops while ensuring that the vehicle is properly maintained, the TSX now has a Maintenance Minder System that automatically monitors the vehicle's operating condition. When maintenance is required, the driver is alerted via a message on the Multi-info display.

The system monitors operating conditions such as oil and coolant temperature and engine speed to determine the proper service intervals. Depending on the operating conditions, oil change intervals can be extended to a maximum of 10,000 miles, potentially sparing the owner considerable money and inconvenience over the life of the car. The system, which can be reset manually by the owner, monitors all normal service parts and systems, including oil and filter, tire rotation, air-cleaner, automatic transmission fluid, spark plugs, timing belt, coolant, brake pads and more.To prevent driver distraction, maintenance alerts are presented when the ignition is first turned on, not while driving.

6-SPEED MANUAL TRANSMISSION

One of the standard transmissions in the TSX is a close-ratio 6-speed manual gearbox. With exceptionally short 45 mm shift throws (most European sedans have shift throws of about 60-65 mm) and a precise, light shifting action, this transmission perfectly complements the car's sporting character. With six gear ratios instead of the more common 5-ratio arrangement, the TSX has closely spaced gears for superior acceleration, yet still has a top gear that allows for a low and efficient cruising rpm.

To reduce weight, the compact transmission case and bell housing are cast of a special magnesium alloy-the first use of this lightweight material in the transmission of an Acura product. This complex casting is seven pounds lighter than the comparable aluminum version, and is highly rigid to damp out noise and vibration. Inside, the gearbox has multi-cone synchronizers on all gears (including reverse) to reduce shifting effort.

A lightweight clutch with low-inertial mass allows the engine to rev quickly, the clutch pedal stroke is short and the effort is comfortably low. A broad and progressive engagement band makes the TSX easy to launch smoothly from a stop. The clutch incorporates a wide-angle clutch-torsion mechanism that reduces the gear rattling sound that is common in many manual-transmission designs.

5-SPEED SEQUENTIAL SPORTSHIFT AUTOMATIC TRANSMISSION

To deliver the smoothness and convenience of an automatic transmission, coupled with the performance and sporting feel of a manual gearbox, the TSX offers a 5-speed Sequential SportShift automatic. With five closely spaced ratios, the automatic transmission helps deliver impressive acceleration performance. An advanced Grade Logic Control System and intelligent shift programming combine with a drive-by-wire throttle control to deliver remarkably swift and smooth shifts and intuitively correct gear selection. To cope with the additional power output, capacity of the second gear clutch pack has been increased.

The TSX automatic transmission reduces shift shock and improves shift smoothness with the use of an industry-leading linear solenoid direct-acting control. The TSX also utilizes an intuitive 5-position shift gate design.

The SportShift transmission can be operated in two different modes: fully automatic or with driver-selected ratios. In automatic mode, its Grade Logic Control System provides smart ratio selection regardless road gradient. With sensors that monitor throttle position, vehicle speed and acceleration/deceleration, the system compares these parameters with a map stored in the transmission computer. Based on this information, the system can determine if the vehicle is on an incline and adjusts the shift schedule for improved climbing power or downhill engine braking.

To switch SportShift to the manual mode, the driver simply moves the selector lever to a special gate to the left of the "Drive" position. When in manual mode, a forward push of the lever selects a higher gear and a rearward pull selects a lower gear. An LED display between the tachometer and speedometer indicates which of the five available gears is in use.

Shift logic is unique in manual mode, with firmer, faster gear change programming that has a feel similar to that of a manual gearbox. Built-in safety override features make SportShift smarter than any conventional manual transmission, however. Under acceleration, the transmission will hold the selected ratio until commanded to upshift. If the driver doesn't make the upshift in time, the engine ECU will cut off the fuel flow to prevent the engine from over-revving. If the high-rpm condition continues for an extended period even after the fuel is cut (as might be possible on a steep downhill) the transmission will upshift automatically to preclude engine damage. Another important safety feature: The logic will not allow a downshift that would cause the engine to over-rev if the driver selects too low of a gear ratio. To preclude the vehicle starting from a stop in a high gear if the driver inadvertently forgets to downshift, the transmission automatically downshifts as the car decelerates to a complete stop.

To accommodate the high-revving engine's horsepower and torque output, a heavy-duty torque converter is used and the countershaft is constructed of high-strength material. To boost efficiency, the transmission has a low-friction clutch and a special super-thin torque converter. The thin torque converter results in a compact transmission unit. Other space saving measures includes a double-row idle gear and a tightly packaged second-gear clutch.

ACTIVE LOCKUP TORQUE CONVERTER

To improve fuel economy and while maintaining a high level of drivability, the 5-speed automatic transmission includes an active lockup torque converter. To handle the increased horsepower, Acura strengthened this torque converter by enlarging the diameter of the boss weld from 25mm to 35mm. With the precise control afforded by a linear solenoid, the system expands the speed and throttle setting range in which lockup can be engaged in the top four gears. The resulting reduction in transmission slippage results in a 2-percent improvement in fuel mileage in both city and highway driving. This transmission's efficiency and taller (higher numerically) final drive ratio helps the TSX deliver exceptional fuel economy as well as increased performance.

COOPERATION BETWEEN 5AT AND DRIVE-BY-WIRE

With the TSX drive-by-wire system, the operation of the automatic transmission and engine are fully integrated, resulting in remarkable shift smoothness, and a significant reduction in shifting time. With this cooperation between engine and transmission, shift time from second to first gear drops from 1.15 second to just 0.7 second-a 40-percent improvement.